$\begingroup$Asking for a list of "exact changes" is too broad for a question. Are you interested in physical changes to mount and connect the payload, or in launch profile changes? Please also note that there is only one operational reusable spacecraft today (OTV, X-37), and no operational reusable LVs. What exact RLV have you got in mind?$\endgroup$
– Deer HunterApr 17 '15 at 18:48

$\begingroup$Forgive me if I was wrong, I had PSLV and GSLV in my mind. And actually I was interested in both physical changes as well as launch profile changes.$\endgroup$
– ManishApr 18 '15 at 2:43

2 Answers
2

The Space Transportation System (aka Space Shuttle) once launched different spacecraft from a reusable launch vehicle. For payloads that were not simply deployed (spring loaded or floated out of the payload bay, or removed with the manipulator arm), two classes of expendable upper stages were used to boost the spacecraft into their final orbits. These were the Payload Assist Modules (PAMs) and the Inertial Upper Stages (IUSes).

This document describes the different services, accomodations, flight sequences, and functions of the PAM / IUS / STS system.

If we can ignore the 'reusable' in the question: commercial launch providers publish a user guide that specifies everything you need to know to make the payload compatible with the launcher.

Compatibility consists of several areas, for example:

the spacecraft has to physically fit inside the payload fairing and has to fit on a payload adapter.

if the spacecraft needs communications, electric power etc. it has to fit the provisions made by the launch provider.

the spacecraft has to withstand the launch environment (vibration and noise levels generated by the launcher).

In some cases, the launch provider can make changes to accommodate your spacecraft, e.g. a new payload fairing (larger or with specific connectors built in) or payload adapter. Changing the launch environment is much harder.

Launch profile changes depend on the final orbit you need, so every launch has a unique profile based on final destination and weight of the spacecraft.
The user guide indicates that the amount of propellant can be changed to suit the mission. I suspect this is only done for the liquid stages; solid stages will get a standard amount of propellant and burn time (if not, they'd have to do custom castings for each launch, which would be expensive).